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Vitamin C can be a helpful ally in the fight to stay healthy during cold and flu season, and while it spring is just around the corner, many places are still seeing the effects of wintertime illnesses. So even now, getting enough C is key, as it supports immune function and has been found to reduce physical and emotional signs of stress. Eat a vitamin C–rich diet and supplement as needed to help keep your levels up when you need it most:

The minimum:The RDA for vitamin C is set to prevent scurvy, a vitamin C–deficiency disease. The daily intake required to prevent scurvy appears to be significantly lower than the amount needed to maximize health and minimize chronic disease risk. Eating 5 to 9 servings of fruit and vegetables daily can meet the 200 mg vitamin C goal and supplements can fill the gaps.

The maximum:Blood levels of vitamin C begin to level off for most people around 200 mg of vitamin C daily from all sources, and consuming more than that did not significantly increase blood levels. Optinions vary on whether vitamin C in excess of this amount is used by the body: there is evidence that it may simply be excreted, but there is also evidence that higher amounts may offer therapeutic effects.

Safety considerations:200 mg of vitamin C daily is considered a safe amount. Most health agencies set a safe upper limit for vitamin C of 1,000 to 2,000 mg per day. Toxicity assessments show no evidence of harm for nearly all adults up to 3,000 mg per day. For people at risk of harm from excess vitamin C, such as those with the blood disorders hemochromatosis and thalassemia, or kidney stones, 200 mg per day appears to be safe.

Diet is best: Broccoli, red peppers, currants, Brussels sprouts, parsley, potatoes, citrus fruit, and strawberries are good sources of vitamin C. Rose hips, harvested from rose bushes and sold as a supplement, are particularly high in vitamin C.